IMPROVING THE TECHNOLOGY FOR PRODUCING FREIGHT WAGON SIDE-FRAME CASTINGS FROM 20GL STEEL

The quality and operational reliability of freight wagon side frames largely depend on the stability of casting processes, particularly moulding sand preparation, mould filling, solidification, and molten metal treatment. This study aims to improve the technology for producing side-frame castings from 20GL steel under the industrial conditions of the "Casting and Mechanical Plant" (QMZ) Joint Stock Company. The research focuses on a large-sized side-frame casting with a mass of approximately 490 kg and wall thicknesses ranging from 70 to 193 mm. Laboratory experiments, industrial trials, metallographic examinations, mechanical testing, statistical analysis, and mathematical modelling were employed. The proposed technological improvements include washing recycled quartz sand, optimizing the moulding mixture composition and preparation time, improving the feeding and solidification conditions, and treating molten steel with aluminium. The results demonstrate an increase in moulding mixture gas permeability from 150 to 250 conventional units, a reduction in internal porosity by 16–18%, and a decrease in surface irregularities by 6–7%. The overall casting rejection rate decreased from 10% to 8.3%. Mechanical test results obtained from 12 melts met the specified requirements, while a finished side frame withstood a static load of 2,850 kN. The proposed integrated approach demonstrates the practical potential of improving the quality and resource efficiency of large-sized 20GL steel castings.